A cancer vaccine for cats

ABSTRACT

The present invention provides an immunogenic composition comprising a nucleic acid that comprises a sequence encoding a cat telomerase deprived of telomerase catalytic activity, or a fragment thereof.

BACKGROUND OF THE INVENTION

Like their human counterparts, cats that live in developed countrieshave seen their life expectancy consistently prolonged. Therefore, theglobal burden of cancers continues to increase largely because of theaging and growing of the cat population.

Cancer incidence rate is estimated to 77 per 10,000 cats. Lymphomas andtumors of the sub-cutaneous tissues, and especially the complex felinefibrosarcoma, are the most frequent of the feline cancerous diseases(Vascellari et al. 2009).

The panel of treatments available against veterinary cancer issubstantially reduced compared with those available in human oncology.

Surgery remains the best way to treat animal tumors. This methodpresents the advantage of being accessible for many veterinarians, and,in many cases, it can be curative. However, to be curative, surgery mustbe bold and in some cases the tumor is too large, too dispersed or justnot accessible enough to be entirely removed. If not totally curative,surgery can still be a palliative solution to improve animal's comfortand prolonged its life expectancy.

Radiotherapy is another important means to treat certain types ofcancers in the veterinary field. It is of particular interest for tumorswhich are hardly accessible for surgery like cerebral tumors.Furthermore, recent studies in humans have demonstrated that ionizingradiation (IR) could act as an immunomodulator by inducing substantialchanges in the tumor microenvironment, including triggering aninflammatory process. Furthermore, the cost and the availability of thematerial make access to radiation therapy complicated for companionanimals.

Chemotherapy is more and more used in animal oncology (Marconato 2011).Taking advantages of medical advances in human cancer therapy, there aremore and more molecules available like vincristine, cyclophosphamide,carboplatin or cisplatin, to treat companion animals. In the veterinaryfield, anticancer drugs are particularly used in the treatment of tumorsderived from hematopoietic tissue (lymphomas, leukemias). For examplethe CHOP protocol, combining cyclophosphamide, doxorubicin, vincristineand prednisone is currently used in the treatment of numerous lymphomas(Chun 2009). Chemotherapeutic agents can be particularly efficient inprolonging the life span of a cancerous animal from a few weeks toseveral months. Interestingly, the side effects dreaded by humanpatients, such as vomiting, diarrhea, hair loss, are usually lessfrequent in companion animals. Unfortunately, most of the timechemotherapy is not curative in pets and the tumor often escapes fromtreatment.

Therefore, just as in human medicine, targeted therapies are indevelopment in veterinary medicine. Other treatments, includingimmunotherapies, are under investigation. These immunotherapeutictreatments are all based on the fact that it is possible to activate theimmune system of the host against cancer cells.

The relationship between the host immune system and cancer is dynamicand complex. Each type of tumor cells harbors a multitude of somaticmutations and epigenetically deregulated genes, the products of whichare potentially recognizable as foreign antigens by immune cells (MUC-1,β-catenin, telomerase . . . ) (Fridman et al. 2012). Growing tumorscontain infiltrating lymphocytes called TILs (Tumor InfiltratingLymphocytes). These killer cells are often ineffective at tumorelimination in vivo but can exert specific functions in vitro, that isto say outside the immunosuppressive tumor microenvironment (Restifo etal. 2012). This is because the tumor stroma contains many suppressiveelements including regulatory T cells (Tregs) and myeloid-derivedsuppressor cells (MDCs); soluble factors such as interleukin 6 (IL-6),IL-10, vascular endothelial growth factor (VEGF), and transforminggrowth factor beta (TGFβ that down modulate antitumor immunity (Finn2008, Hanahan and Weinberg 2011). Consequently, the choice of apertinent tumor associated antigen (TAA) and the bypass of cancerassociated immunosuppression are two critical points for a therapeuticvaccine to succeed (Disis et al. 2009).

Recent introduction of active cancer immunotherapy (also referred tocancer vaccines) in the clinical cancer practice emphasizes the role ofimmune responses in cancer prognosis and has led to a growing interestto extend this approach to several human and companion animal cancers(Dillman 2011, Topalian et al. 2011) (Jourdier et al. 2003).

In this context, there is still a need for an innovative cancer vaccinestrategy for cats, which would overcome the challenge of breakingtolerance and inducing an immune response in the animal.

SUMMARY OF THE INVENTION

The inventors now propose a cancer vaccine strategy for cats, based onthe telomerase reverse transcriptase (TERT).

A subject of the invention is thus an immunogenic composition comprisinga nucleic acid that comprises a sequence encoding (i) a cat TERTdeprived of telomerase catalytic activity, or (ii) a fragment thereof.The nucleic acid is preferably DNA, preferably in form of a plasmid.

In a preferred embodiment, the nucleic acid that comprises a sequenceencoding a cat telomerase reverse transcriptase (TERT) deprived oftelomerase catalytic activity, wherein the sequence encoding catTERT isfurther deprived of a nucleolar localization signal.

In a particular embodiment, the nucleic acid further comprises a non-catTERT antigenic fragment.

A further subject of the invention is a nucleic acid that comprises asequence encoding (i) a cat TERT deprived of telomerase catalyticactivity, or (ii) a fragment thereof, and optionally further comprises anon-cat TERT antigenic fragment.

The immunogenic composition or the nucleic acid is useful in triggeringan immune response in a cat, against cells that overexpress telomerase,such as dysplasia cells, tumor cells, or cells infected by an oncovirus.

The immunogenic composition or the nucleic acid is thus particularlyuseful in treating a tumor in a cat, preferably by intradermal orintramuscular route.

Such treatment can be referred to as an active immunotherapy or atherapeutic vaccination, as it triggers an immune response against thetumor, especially a cytotoxic CD8 T cell response, along with a specificCD4 T cell response.

The invention makes it possible to induce dTERT specific responses incats with neoplasias and so can be used for immunotherapeutic treatmentsof the neoplasias in a clinical setting. The invention is also useful toinduce dTERT specific responses in healthy cats that could be at riskfor cancer, e.g. by genetic predisposition, or in healthy cats from acertain age (e.g. of 12 years or more, preferably more than 14 yearsold) so as to prevent the onset of cancer.

Generally speaking, the treatment of the invention may induce long termimmune memory responses in healthy dogs, dogs at risk of developing acancer and those presenting a cancer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A shows pUF2 nucleotide sequence (SEQ ID NO: 1) and correspondingamino acid sequence comprising cat TERT amino acid sequence. (SEQ ID NO:2).

The plasmid pUF2 encodes a cat TERT (cTERT) protein comprising about 95%from the cat TERT and about 5% from the dog TERT sequence. Exon 1encoding the extreme amino terminus of the cat telomerase genes remainsunknown. It is estimated that 47 amino acids (141 bases) are missing.The nucleotide sequence encoding 3 key amino acids in the catalytic siteof the protein have been deleted (VDD). Moreover, the sequencecontrolling the importation into the nucleoli (Nucleolar addressingsignal) has been deleted (nucleotide sequence encoding 47 first AminoAcids in the N ter sequence of cTERT protein). The DNA sequence encodingthe human ubiquitin has been added upstream the cTERT sequence. Thepresence of the ubiquitin protein enhances the addressing of the cTERTprotein to the proteasome and increases class I presentation of derivedpeptides. However, as the human and cat ubiquitin sequences areidentical at the protein level, there is no biological incompatibility.Downstream the cTERT sequence, the sequence of the V5 peptide of the fluwas inserted to facilitate the detection of the protein

Nucleotides 1-6 HindIII restriction site for subcloningNucleotides 13-240 ubiquitinNucleotides 241-438 dog TERT (5.5% of TERT sequences)

Nucleotides 439-3444 cat TERT Nucleotides 3517-3558 SV5 V5 tag

Nucleotides 3586-3588 two stop codonsNucleotides 3495-3500 Xba1 restriction site for subcloningNucleotides 2655-2656 inactivating deletion of 9 by encoding VDDresidues

FIG. 1B shows pCDT nucleotide sequence (SEQ ID NO: 3) and correspondingamino acid sequence containing cat/dog hybrid TERT amino acid sequence(SEQ ID NO: 4).

The plasmid pCDT encode the cat/dog hybrid TERT (hyTERT) comprising54.4% from the cat TERT and 35.9% from the dog TERT sequence. Thenucleotide sequence encoding 3 key amino acids in the catalytic site ofthe protein have been deleted (VDD). Moreover, the sequence controllingthe importation into the nucleoli (Nucleolar addressing signal) has beendepleted (nucleotide sequence encoding 45 first Amino Acids in the Ntermsequence of hyTERT protein). The DNA sequence encoding the humanubiquitin has been added upstream the hyTERT sequence. The presence ofthe ubiquitin protein enhances the addressing of the hyTERT protein tothe proteasome and increases class I presentation of the derivedpeptides. Downstream the hyTERT sequence, the sequence of the V5 peptideof the flu was inserted to facilitate the detection of the protein.

Nucleotides 1-6 HindIII restriction site for subcloningNucleotides 13-240 ubiquitinNucleotides 241-1413 dog TERT (35.9% of TERT sequences)Nucleotides 1414-3297 cat TERT (54.4% of TERT sequences)Nucleotides 3298-3456 dog TERT last exonNucleotides 3457-3510 influenza A2 epitope

Nucleotides 3511-3552 SV5 V5 tag

Nucleotides 2667-2668 inactivating deletion of 9 by encoding VDDresiduesNucleotides 3553-3558 two stop codonsNucleotides 3559-3564 Xba1 restriction site for subcloning

FIG. 1C shows a simplified map of pcDNA3.1 expression plasmid into whichthe cat/dog hybrid TERT nucleic acid sequence was cloned.

FIG. 2 shows that pDNA constructs are safe (Trapeze), (A) Lysatesobtained from CrFK cells transfected with hTERT (human telomerase fullyactive), pCDT or pUF2 plasmids were analyzed for telomerase activity bythe TRAP assay. The level of telomerase activity is shown as relativetelomerase activity compared with that of control template measured ineach kit. All samples at 2.1 μg protein concentration were measured intriplicate, error bars are standard error of the mean (SEM) (**P=0.0020,hTERT vs pUF2 unpaired t test) FIGS. 3A and 3B show specific IFNγ+ CD8and CD4 T-cell responses against H2 restricted hyTERT peptides in miceimmunized with pCDT.

Seven week-old female mice were immunized intradermally (ID) orintramuscularly (IM) with either 100 μg pCDT plasmid or PBS at day 0 andboost 14 days later. Ten day post-boost, spleens were harvested.Splenocytes were Ficoll-purified and stimulated in triplicates with 5μg/mL of relevant peptides for 19 hours. Spots were revealed with abiotin-conjugated detection antibody followed by streptavidin-AP andBCIP/NBT substrate solution.

(A) Plasmid vaccinated groups were composed of five C57/Bl6 mice, andcontrol groups, of three mice. Splenocytes were stimulated with class Ipeptides p580, p621 and p987. Results show the frequency of peptidespecific IFN-γ producing CD8 T cells.

(B) Plasmid vaccinated groups were composed of 9 Balb/cBy mice immunizedIM and 5 ID. Control groups of 8 Balb/cBy mice injected IM and 4 ID.Splenocytes were stimulated with class II peptides p951, p1105, p1106and p1109. Results show the frequency of peptide specific IFN-γproducing CD4 T cells.

Results are the mean±standard deviation. Mann Whitney non parametrictest, * p-value<0.05, **: p-value<0.01.

FIGS. 4A and 4B show a hyTERT specific cytotoxic T-lymphocyte (CTL)response in mice immunized with pCDT plasmid, measurable in vivo byelimination of transferred target cells pulsed with H2 restricted hybridTERT peptides.

7 week-old C57/Bl6 female mice were immunized ID or IM with 100 μg pCDTplasmid at day 0 and day 14 post-priming. At day 9 post-boost injection,syngeneic splenocytes, pulsed with individual dTERT peptides restrictedto H2 (either p987 or p621) or left unpulsed were labeled withcarboxyfluorescein-diacetate succinimidyl ester (CFSE) at threedifferent concentrations: high=1 μM (987), medium=0.5 μM (621) andlow=0.1 μM (unpulsed). The same number of high, medium or low CFSElabeled cells was transferred IV to vaccinated mice. After 15-18 hours,the disappearance of peptide-pulsed cells was determined byfluorescence-activated cell-sorting analysis in the spleen. Thepercentage of specific lysis was calculated by comparing the ratio ofpulsed to un-pulsed cells in vaccinated versus control mice.

(A) Example of the in vivo CTL assay showing the elimination of targetcells pulsed with p621 peptide (High, H) or p987 peptide (Medium, M) inthe spleen of a mouse vaccinated ID (left panel) with pCDT. No suchdisappearing is observed in control mice injected ID with PBS 1× (rightpanel).

(B) Percentage of specific lysis for each mouse against each individualpeptide in the spleen after IM or ID vaccination with pCDT. Horizontalbars show average percentage of lysis per peptide and per immunizationroute. Standard deviations are also plotted. Representative data from 2independent experiments (n=10 individual animals/group). Kruskal-Wallisanalysis with Dunn's multiple comparison test, * p<0.1, *** p<0.001, ns:not significant. Statistical significance is set at p-value<0.05.

FIGS. 5A and 5B show IFNγ+ specific CD8 and CD4 T-cell responses againstH2 restricted cat TERT peptides in mice immunized with pUF2.

Seven week-old female mice were immunized ID or IM with either 100 μgpUF2 plasmid or PBS at day 0 and boost 14 days later. Ten days postboost, spleens were harvested. Splenocytes were Ficoll-purified andstimulated in triplicates with 5 μg/mL of relevant peptides for 19hours. Spots were revealed with a biotin-conjugated detection antibodyfollowed by streptavidin-AP and BCIP/NBT substrate solution. Vaccinatedgroups were composed of six C57/Bl6 mice, and control groups, of threemice. Splenocytes were stimulated with class I peptides p580, p621 andp987. Results show the frequency of peptide specific IFN-γ producing CD8T cells. Vaccinated groups were composed of six Balb/cBy mice, andcontrol groups, of three mice. Splenocytes were stimulated with class IIpeptides p1105 and p1106. Results show the frequency of peptide specificIFN-γ producing CD4 T cells.

Results are the mean±standard deviation. Mann Whitney non parametrictest, * p-value<0.05, **: p-value<0.01.

FIGS. 6 A and B show that mice immunized with pUF2 are able to lyse H2restricted cat TERT peptide-loaded on target cells in vivo

7 week-old C57/Bl6 female mice were immunized ID or IM with 100 μg pCDTplasmid at day 0 and day 14 post-priming. At day 9 post-boost injection,syngeneic splenocytes, pulsed with individual dTERT peptides restrictedto H2 (either p987 or p621) or left unpulsed were labeled withcarboxyfluorescein-diacetate succinimidyl ester (CFSE) at threedifferent concentrations: high=1 μM (987), medium=0.5 μM (621) andlow=0.1 μM (unpulsed). The same number of high, medium or low CFSElabeled cells was transferred IV to vaccinated mice. After 15-18 hours,the disappearance of peptide-pulsed cells was determined byfluorescence-activated cell-sorting analysis in the spleen. Thepercentage of specific lysis was calculated by comparing the ratio ofpulsed to un-pulsed cells in vaccinated versus control mice.

(A) Example of the in vivo CTL assay showing the elimination of targetcells pulsed with either p621 or p987 peptides in the spleen of a mousevaccinated ID (left panel). No such disappearing is observed in controlmice (right panel) or in certain mice vaccinated IM (middle panel).H=high, M=Medium, L=Low.

(B) Percentage of specific lysis for each mouse against each individualpeptide in the spleen after IM or ID vaccination with pUF2. Horizontalbars show average percentage of lysis per peptide and per immunizationroute. Standard deviations are also plotted. Representative data fromn=5 animals/group. Kruskal-Wallis analysis with Dunn's multiplecomparison test, ns: not significant. Statistical significance is set atp-value<0.05.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The telomerase consists of an RNA template and protein componentsincluding a reverse transcriptase, designated “Telomerase ReverseTranscriptase” (TERT), which is the major determinant of telomeraseactivity. Unless otherwise specified, in the present specification, theterm “telomerase” refers to TERT.

In the present invention, the term “cat TERT” refers to the TERTsequence of any domestic cat (also designated as Felis catus or Felissilvestris catus). Partial molecular cloning of the cat TERT gene (237bp of mRNA) has been reported by Yazawa et al, 2003. The inventorsherein provide a longer sequence of Felis catus TERTPartial amino acidsequences of cat TERT are shown as SEQ ID NO:5 and SEQ ID NO:6.

The invention can also make use of non-cat telomerase (TERT) sequence,which can be from any human or non-human mammal, e.g. from dog. The term“dog TERT” refers to the TERT sequence of any domestic dog (alsodesignated Canis familiaris or Canis lupus familiaris).

A dog TERT mRNA sequence is available with NCBI accession numberNM_(—)001031630 (XM_(—)545191). Dog TERT amino acid sequence is shown asSEQ ID NO: 9.

The “telomerase catalytic activity” refers to the activity of TERT as atelomerase reverse transcriptase. The term “deprived of telomerasecatalytic activity” means that the nucleic acid sequence encodes amutant TERT, which is inactive.

The term “hybrid” or “chimeric” amino acid or nucleotide sequence meansthat part of the sequence originates from one animal species and atleast another part of the sequence is xenogeneic, i.e. it originatesfrom at least one other animal species.

When referring to a protein, the term “fragment” preferably refers tofragment of at least 10 amino acids, preferably at least 20 amino acids,still preferably at least 30, 40, 50, 60, 70, 80 amino acid fragments.

In the context of the invention, the term “antigenic fragment” refers toan amino acid sequence comprising one or several epitopes that induce Tcell response in the animal, preferably cytotoxic T lymphocytes (CTLs).An epitope is a specific site which binds to a T-cell receptor orspecific antibody, and typically comprises about 3 amino acid residuesto about 30 amino acid residues, preferably 8 or 9 amino acids as far asclass I MHC epitopes are concerned, and preferably 11 to 25 amino acidsas far as class II MHC epitopes are concerned.

The term “immunogenic” means that the composition or construct to whichit refers is capable of inducing an immune response upon administration(preferably in a cat). “Immune response” in a subject refers to thedevelopment of a humoral immune response, a cellular immune response, ora humoral and a cellular immune response to an antigen. A “humoralimmune response” refers to one that is mediated by antibodies. A“cellular immune response” is one mediated by T-lymphocytes. It includesthe production of cytokines, chemokines and similar molecules producedby activated T-cells, white blood cells, or both. Immune responses canbe determined using standard immunoassays and neutralization assays fordetection of the humoral immune response, which are known in the art. Inthe context of the invention, the immune response preferably encompassesstimulation or proliferation of cytotoxic CD8 T cells and/or CD4 Tcells.

As used herein, the term “treatment” or “therapy” includes curativetreatment. More particularly, curative treatment refers to any of thealleviation, amelioration and/or elimination, reduction and/orstabilization (e.g., failure to progress to more advanced stages) of asymptom, as well as delay in progression of the tumor or dysplasia, orof a symptom thereof.

As used herein, the term “prevention” or “preventing” refers to thealleviation, amelioration and/or elimination, reduction and/orstabilization (e.g., failure to progress to more advanced stages) of aprodrome, i.e. any alteration or early symptom (or set of symptoms) thatmight indicate the start of a disease before specific symptoms occur. Acell that “overexpresses telomerase” refers to a cell in a subject,which either expresses telomerase, e.g. upon mutation or infection,whereas it does usually not, under normal conditions, or to a cell in asubject which expresses a higher level of telomerase (e.g. upon mutationor infection), when compared to normal conditions. Preferably the cellthat overexpresses telomerase shows an increase of expression of atleast 5%, at least 10%, at least 20%, 30%, 40%, 50%, 60%, 70%, 80%, ormore.

Nucleic Acid Constructs

It is herein provided a nucleic acid that comprises a sequence encoding(i) a cat telomerase reverse transcriptase (TERT) deprived of telomerasecatalytic activity, or (ii) a fragment thereof.

The nucleic acid may be DNA or RNA, but is preferably DNA, stillpreferably double stranded DNA.

As a first safety key, the TERT sequence is deprived of telomerasecatalytic activity. In a preferred embodiment, the sequence that encodescat TERT contains mutations that provide inactivation of the catalyticactivity. The term “mutation” include a substitution of one or severalamino acids, a deletion of one or several aminoacids, and/or aninsertion of one of several amino acids. Preferably the sequence shows adeletion, preferably a deletion of amino acids VDD, as shown in FIG. 1Aor 1B.

As a second safety key, the sequence encoding cat TERT can further bedeprived of a nucleolar localization signal. This nucleolar localizationsignal is correlated with the enzymatic activity of TERT. This signalcorresponds to the N-terminal 47 amino acids at the N-terminus of theTERT sequence.

Preferably the sequence encoding cat TERT is deleted of N-terminal 47amino acids. Cat TERT sequence fragments deleted of amino acids VDD andof the N-terminal nucleolar localization signal are shown as SEQ ID NO:7and SEQ ID NO:8.

In a particular embodiment, the nucleic acid may encode cat TERTsequence or a fragment thereof only, which preferably corresponds to atleast 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or at least 95% ofthe cat TERT sequence deleted of the N-terminal 47 amino acids.

Preferably, the nucleic acid encodes a cat TERT sequence comprising, orconsisting of, SEQ ID NO: 5, 6, 7 or 8.

The nucleic acid may further encode a non-cat TERT antigenic fragment.This embodiment is preferred, to favor breakage of tolerance towards aself-antigen, and induce an efficient immune response along, with animmune memory response in the cat. The presence of non-cat TERTfragment(s) advantageously engages certain subtypes of CD4⁺ T cells,providing help for anti-tumor immunity, and reversing potentialregulation via the secretion of Th1 cytokines.

The cat and non-cat TERT sequences or fragments thereof are preferablyfused, to be expressed as a hybrid or chimeric protein. Alternatively,the cat and non-cat TERT sequences or fragments thereof may beseparated, but carried on the same vector, e.g. the same plasmid.

Preferably the non-cat TERT antigenic fragment corresponds to a fragmentabsent or eliminated from the cat TERT sequence, to the extent it doesnot complement the loss of catalytic activity or the loss of thenucleolar localization signal.

The cat TERT sequence, or fragment thereof, can represent at least 50%,55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or at least 95% of all TERTsequences in the nucleic acid, plasmid, or other vector.

In a preferred embodiment, the cat TERT sequence or fragment representsat least 90% of the hybrid or chimeric TERT protein.

In another embodiment, the cat TERT sequence or fragment represents atleast 60% of the hybrid or chimeric TERT protein.

The non-cat TERT antigenic fragment preferably originates from a dogTERT sequence.

The non-cat TERT antigenic fragment is advantageously processed bydendritic cells, thereby generating T cell help.

In a preferred embodiment, the invention employs a nucleic acid thatencodes a protein sequence selected from the group consisting of SEQ IDNO: 2, 4, 5, 6, 7, or 8.

Such nucleic acid may comprise a sequence selected from the groupconsisting of SEQ ID NO: 1, 3, or nucleotides 241-3444, or 382-3444 or439-3444 of SEQ ID NO:1, or nucleotides 1408-3297 or 1414-3297 or241-3456 of SEQ ID NO: 3.

In a particular embodiment, the nucleic acid may further encode aprotein which enhances the addressing of the TERT protein to theproteasome and increases class I presentation of the derived peptides.Said protein may be preferably ubiquitin or it may be any chaperonprotein, e.g. calreticulin.

Genetic Constructs, Immunogenic Compositions and Administration

Preferably, the nucleic acid is a genetic contrast comprising apolynucleotide sequence as defined herein, and regulatory sequences(such as a suitable promoter(s), enhancer(s), terminator(s), etc.)allowing the expression (e.g. transcription and translation) of theprotein product in the host cell or host organism.

The genetic constructs of the invention may be DNA or RNA, and arepreferably double-stranded DNA. The genetic constructs of the inventionmay also be in a form suitable for transformation of the intended hostcell or host organism, in a form suitable for integration into thegenomic DNA of the intended host cell or in a form suitable forindependent replication, maintenance and/or inheritance in the intendedhost organism. For instance, the genetic constructs of the invention maybe in the form of a vector, such as for example a plasmid, cosmid, YAC,a viral vector or transposon. In particular, the vector may be anexpression vector, i.e. a vector that can provide for expression invitro and/or in vivo (e.g. in a suitable host cell, host organism and/orexpression system).

In a preferred but non-limiting aspect, a genetic construct of theinvention comprises i) at least one nucleic acid of the invention;operably connected to ii) one or more regulatory elements, such as apromoter and optionally a suitable terminator; and optionally also iii)one or more further elements of genetic constructs such as 3′- or 5′-UTRsequences, leader sequences, selection markers, expressionmarkers/reporter genes, and/or elements that may facilitate or increase(the efficiency of) transformation or integration.

In a particular embodiment, the genetic construct can be prepared bydigesting the nucleic acid polymer with a restriction endonuclease andcloning into a plasmid containing a promoter such as the SV40 promoter,the cytomegalovirus (CMV) promoter or the Rous sarcoma virus (RSV)promoter. In a preferred embodiment, the TERT nucleic acid sequences areinserted into a pcDNA3.1 expression plasmid (see FIG. 1C) or pcDNA3.1TOPO-V5. Other vectors include retroviral vectors, lentivirus vectors,adenovirus vectors, vaccinia virus vectors, pox virus vectors andadenovirus-associated vectors.

Compositions can be prepared, comprising said nucleic acid or vector.The compositions are immunogenic. They can comprise a carrier orexcipients that are suitable for administration in cats (i.e. non-toxic,and, if necessary, sterile). Such excipients include liquid, semisolid,or solid diluents that serve as pharmaceutical vehicles, isotonicagents, stabilizers, or any adjuvant. Diluents can include water,saline, dextrose, ethanol, glycerol, and the like. Isotonic agents caninclude sodium chloride, dextrose, mannitol, sorbitol, and lactose,among others. Stabilizers include albumin, among others. Any adjuvantknown in the art may be used in the vaccine composition, includingoil-based adjuvants such as Freund's Complete Adjuvant and Freund'sIncomplete Adjuvant, mycolate-based adjuvants, bacteriallipopolysaccharide (LPS), peptidoglycans, proteoglycans, aluminumhydroxide, saponin, DEAE-dextran, neutral oils (such as miglyol),vegetable oils (such as arachis oil), Pluronic® polyols.

The nucleic acid or composition can be administered directly or they canbe packaged in liposomes or coated onto colloidal gold particles priorto administration. Techniques for packaging DNA vaccines into liposomesare known in the art, for example from Murray, 1991. Similarly,techniques for coating naked DNA onto gold particles are taught in Yang,1992, and techniques for expression of proteins using viral vectors arefound in Adolph, 1996.

For genetic immunization, the vaccine compositions are preferablyadministered intradermally, subcutaneously or intramuscularly byinjection or by gas driven particle bombardment, and are delivered in anamount effective to stimulate an immune response in the host organism.In a preferred embodiment of the present invention, administrationcomprises an electroporation step, also designated herein by the term“electrotransfer”, in addition to the injection step (as described inMir 2008, Sardesai and Weiner 2011).

The compositions may also be administered ex vivo to blood or bonemarrow-derived cells using liposomal transfection, particle bombardmentor viral transduction (including co-cultivation techniques). The treatedcells are then reintroduced back into the subject to be immunized.

While it will be understood that the amount of material needed willdepend on the immunogenicity of each individual construct and cannot bepredicted a priori, the process of determining the appropriate dosagefor any given construct is straightforward. Specifically, a series ofdosages of increasing size, starting at about 5 to 30 μg, or preferably20-25 μg, up to about 500 μg for instance, is administered to thecorresponding species and the resulting immune response is observed, forexample by detecting the cellular immune response by an Elispot assay(as described in the experimental section), by detecting CTL responseusing a chromium release assay or detecting TH (helper T cell) responseusing a cytokine release assay.

In a preferred embodiment, the vaccination regimen comprises one tothree injections, preferably repeated three or four weeks later.

In a particular embodiment, the vaccination schedule can be composed ofone or two injections followed three or four weeks later by at least onecycle of three to five injections.

In another embodiment, a primer dose consists of one to threeinjections, followed by at least a booster dose every year, or every twoor years for instance.

Prevention or Treatment of Tumors

The nucleic acid or immunogenic composition as described above is usefulin a method for preventing or treating a tumor in a cat.

A method for preventing or treating a tumor in a cat is described, whichmethod comprises administering an effective amount of said nucleic acidor immunogenic composition in a cat in need thereof. Said nucleic acidor immunogenic composition is administered in an amount sufficient toinduce an immune response in the cat.

The tumor may be any undesired proliferation of cells, in particular abenign tumor or a malignant tumor, especially a cancer.

The cancer may be at any stage of development, including the metastaticstage. However preferably the cancer has not progressed to metastasis.

In particular the tumor may be selected from the group consisting of alymphoma or lymphosarcoma (LSA), adenoma, lipoma, myeloproliferativetumor, melanoma, squamous cell carcinoma, mast cell tumor, osteosarcoma,fibrosarcoma, lung tumor, brain tumor, nasal tumor, liver tumor, andmammary tumor.

Lymphoma or lymphosarcoma (LSA) is common among cats with FelineLeukemia Virus (FeLV) infections. LSA affects the intestines and otherlymphatic tissues (commonly the abdominal organs).

Adenomas are tumors that affect sebaceous glands predominantly in thelimbs, the eyelids and the head. They are also commonly-found in theears (and ear canals) of cats and may lead to the development ofhyperthyroidism.

Lipomas are tumors that occur within the fatty tissues and reside assoft, fluctuant round masses that adhere tightly to surrounding tissue(typically to organs and the membrane linings of body cavities).

Myeloproliferative tumors generally are genetic disorders. It can affectthe bone marrow, white blood cells, red blood cells, and platelets.

Melanomas manifest as basal cell tumors. These tumors are usually benignin nature. They are commonly found around the neck, head, ears, andshoulder regions and can be treated through chemotherapy or radiationtherapy.

Squamous cell carcinomas affect areas that lack natural pigmentation(oral cavity, tonsils, lips, nose, eyelids, external ear, limbs, toesand nails), or areas that are under constant trauma and irritation. Oralsquamous carcinomas are the most common.

Mast cell tumors are either sole or multiple skin nodules that may beulcerated and pigmented. They can be located on any part of the cat'sbody.

Osteosarcoma are tumors that mainly affect the joints, bones and lungs.

Fibrosarcomas arise from the fibrous tissues just beneath the skin.Fibrosarcomas generally develop in muscle or in the connective tissue ofthe body.

Generally speaking, lung tumors, brain tumors, nasal tumors, livertumors, mammary tumors are encompassed.

In a particular embodiment, the vaccination according to the inventionmay be combined with conventional therapy, including chemotherapy,radiotherapy or surgery. Combinations with adjuvant immunomodulatingmolecules such GM-CSF or IL-2 could also be useful.

The Figures and Examples illustrate the invention without limiting itsscope.

EXAMPLES

The inventors have constructed DNA vaccines encoding an inactivated formof cat TERT and a cat/dog hybrid TERT (Example 1), and have assessedtheir functionality, safety and immunogenicity.

They have demonstrated that the plasmids were correctly processed invitro after transfection in mammalian cells and that the plasmid productof expression (TERT protein) was well expressed. Moreover, no enzymaticactivity was detected and TERT proteins were found excluded for thetransfected cells nucleoli, which evidences safety of the constructs(Example 2).

Then, the plasmids were found to be immunogenic and to elicit specificefficient CD8 T cells and CD4 T cells in mice (Example 3).

Example 1 Construction of the DNA Plasmids

In all constructs, the TERT sequence is preceded by a DNA sequenceencoding the human-ubiquitin. The presence of the Ubiquitin willincrease the addressing of the TERT protein to the proteasome andincrease the class I presentation pathway of TERT derived peptides. TERTsequence is followed by the sequence of the influenza protein V5 tofacilitate future purification or detection of the fusion protein byWestern Blot or histochemistry for example. The DNA sequence coding forthe TERT protein has been deleted of 47 Amino-acids in the N-Termregion, which encodes the nucleolar importation signal. Moreover, threeamino-acids have been removed in the catalytic site of TERT (VDD), toinhibit the protein enzymatic activity. pUF2 encodes 95% of the cat TERTand 5% of the canine TERT sequence (FIG. 1A), pCDT encodes 54.4% of thecat TERT sequence and 35.9% of the dog TERT sequence (FIG. 1B).

All TERT DNA sequences were synthetized from Genecust (Dudelange,Luxembourg). Then they were cloned into the pCDNA3.1 or pcDNA3.1 TOPO-V5expression plasmid provided by Life technologies SAS (Saint-Aubin,France) using the HindIII and XbaI restriction sites (see FIG. 1C).Plasmids were stored at −20° C., in PBS 1×, at a concentration of 2mg/mL prior use. The backbone plasmid was used as empty vector forwestern blot and Trap-Assay experiments. It consists of the pcDNA3.1backbone plasmid deprived of the transgene protein DNA sequence (TERT).

Example 2 Functionality and Safety of the Plasmids 2.1. Materials andMethods Cell Culture

The 293T cell line used for transfection assays and immune-fluorescenceexperiments were kindly provided by Pr Simon Wain-Hobson (PasteurInstitute). CrFK cells were kindly provided by Pr J. Richardson (EcoleVétérinaire de Maison-Alfort). Cells were grown at 37° C., 5% CO₂₋ inDulbecco's Modified Eagle Medium (DMEM) supplemented with 10%heat-inactivated Fetal Calf Serum (FCS), 1% sodium-pyruvate, 1%penicillin-streptomycin pyruvate and 0, 1% β-mercaptoethanol. Allcomponents of the culture medium were purchased from Life technologiesSAS (Saint-Aubin, France).

Transfection Assays

Transfection of 293T cells were performed with either pCDT or pUF2plasmids using the JetPRIME® transfection kit (Polyplus-transfection SA,Illkirch, France) according to manufacturer's instruction. In a 6-wellplate, 400 000 HeLa cells or 293T cells per well were seeded in 2 mL ofDMEM culture medium, and cultured 24 hours at 37° C., 5% CO₂ priortransfection. For each well, 2 μg of each plasmid diluted in 200 μL ofjetPRIME® buffer, or 200 μL of jetPRIME® buffer only with respectively 4μL of jetPRIME® agent were drop onto the cells. Transfection medium wereremoved 4 hours later and replaced by 2 mL of DMEM culture medium. Cellswere put at 37° C., 5% CO2 and recovered for analysis 24 hours later.

Western Blots

Transfected 293 T cells were lysed on ice with radioimmunoprecipitationassay (RIPA) lysis buffer (RIPA Buffer, Sigma Aldrich chimie SARL,Saint-Quentin Fallavier, France) containing protease inhibitors cocktail(Complete EDTA-free, Roche Diagnostic, Indianapolis, USA) for 10-20minutes. Then, suspension was centrifuged 15 minutes at 14000 rpm at 4°C. in order to remove cellular debris. The supernatants were harvestedand the protein concentration was measured using the Bradford method.Protein samples were denatured 5 minutes at 95° C., separated onNu-PAGE® Novex 4-12% Bis-Tris gels (Invitrogen, Carlsbad, USA) andtransferred to PVDF membranes (iBlot® transfer stack, Invitrogen,Carlsbad, USA) using the iBlot® device (Invitrogen, Carlsbad, USA). Themembrane was cut approximately at 60 kDa. First, the upper part membranewas probed with an anti-V5 antibody (Invitrogen, Carlsbad, USA) whilethe other part was probed with an anti-β-actin antibody (Sigma Aldrichchimie SARL, Saint-Quentin Fallavier, France), then samples wererevealed by an ECL (Enhanced chemiluminescence) anti-mouse Horse RadishPeroxidase (HRP) linked antibody (GE Healthcare, Vélizy, France)).Immunoblot signals were reveled using 18×24 films and the correspondingcassette both products purchased from GE healthcare (Buckinghamshire,UK).

Immunofluorescence and Microscopy

293T cells were seeded on 8-well Lab-Tek® chamber slides (Sigma Aldrichchimie SARL, Saint-Quentin Fallavier, France) at 20·10³ cells/well in200 μL of culture medium and incubated overnight at 37° C. The next day,culture medium was discarded. Ten μL of a mix solution containing 1 μgof either pCDT or pUF2 plasmid, 50 μL of OptiMEM (Life technologies SAS,Saint-Aubin, France) and 2.5 μL of Fugene HD (Promega France,Charbonnières-les-bains, France) were added to the correspondingchamber. As control, 20·10³ HeLa cells were incubated with the 10 μL ofthe same mix without plasmid. Chamber slides were left in the incubatorfor 24 hours. Transfected 293T cells were carefully washed with PBS 1×and 200 μL 2% PFA were added to each well for 10 minutes at +4° C., inorder to fix and permeabilize the cells. Then wells were washed twotimes with PBS 1×0.05% Tween®20 and 293T cells were incubated 30 minutesat room temperature with 200 μL of Blocking solution (0.5% TritonX100;3% BSA; 10% Goat Serum). Eventually, wells were incubated for 1.5 hoursat room temperature with a primary mouse anti-V5 antibody (Lifetechnologies SAS, Saint-Aubin, France) diluted in blocking solution at1/200, with slight agitation. After three washes in PBS 1×0.05%Tween®20, a secondary goat anti-mouse-Alexa Fluor 488® antibody (Lifetechnologies SAS, Saint-Aubin, France) diluted in blocking solution(1/500) was put in the wells for 45 minutes at room temperature awayfrom light and under slight agitation. Wells were washed three timeswith PBS 1×0.05% Tween®20 and mounted with the Vectashield® mountingmedium containing DAPI (Vector laboratories, Peterborough, UK). Slideswere analyzed with a fluorescence microscope (Axio observer Z1, CarlZeis MicroImaging GmbH, Jena, Germany) equipped with an image processingand analysis system (Axiovision, Carl Zeis MicroImaging GmbH, Jena,Germany).

Trap-Assay

Telomerase activity was measured by the photometric enzyme immunoassayfor quantitative determination of telomerase activity, utilizingtelomeric repeat amplification protocol (TRAP) (Yang et al. 2002).

CrFK (Crandell Rees Feline Kidney) telomerase-negative cells (Yazawa etal., 2003) were transfected with plasmids encoding pUF2 or pCDT TERTconstructs. Briefly, 24 hours after transfection, CrFK cells wereharvested by mechanical scraping and then washed twice with 1 mL PBS andpelleted by centrifugation 5 minutes at 3000 g, at 4° C. Telomeraseactivity was assessed by TRAP-ELISA assay using the TeloTAGGG TelomerasePCR ELISAPLUS kit (Roche Diagnostics, Germany) according to themanufacturer's instructions. The protein concentration in the cellextract was measured by the Bradford method (Bio-Rad Laboratories).Three microliters of the cell extract (equivalent to 2.1, 0.21, 0.021μg) was incubated in a Polymerase Chain reaction (PCR) mixture providedin the kit. The cycling program was performed with 30 minutes primerelongation at 25° C. and then the mixture was subjected to 30 cycles ofPCR consisting of denaturation at 94° C. for 30 sec, annealing at 50° C.for 30 sec, polymerization at 72° C. for 90 sec and final extension at72° C. for 10 minutes. 2.5 μl of amplification product was used forELISA according to the manufacturer's instructions. The absorbance at450 nm (with a reference of 690 nm) of each well was measured usingDynex MRX Revelation and Revelation TC 96 Well Microplate Reader.Telomerase activity was calculated as suggested in the kit's manual andcompared with a control template of 0.1 amol telomeric repeats,representing a relative telomerase activity (RTA) of 100. Inactivatedsamples and lysis buffer served as negative controls.

2.2. Results

New TERT Encoding Plasmids are Functional In Vitro after Transfection

The functionality of the new plasmid constructs is shown by the presenceof the plasmid encoded TERT protein in the total protein lysate of pCDTor pUF2 transfected cells in vitro. The inventors performed western-blotassays on the total protein lysate of 293T cells plasmids transfectedwith pCDT or pUF2 (24 h after transfection). As the TERT proteinsequence encoded by each plasmid was tagged with the V5 proteinsequence, anti-V5 antibody coupled with Horse Radish Peroxidase (HRP)was used to reveal the presence of the fusion protein of interest.

A highly positive V5 specific-signal was detected 24 h aftertransfection in the protein lysate of pCDT or pUF2 transfected cells.The size of the protein band detected corresponds to the different TERTprotein encoded by the plasmids which molecular weight is 123 kDa.Moreover no V5 specific signal was detected in untreated or emptyplasmid transfected cells. The inventors demonstrated that pUF2 and pCDTplasmids were correctly processed in vitro after transfection inmammalian cells and that the plasmid product of expression (TERTprotein) was well expressed.

New TERT Encoding Plasmids Express a Non-Functional Enzyme of whichCellular Expression is Excluded from the Nucleoli after In VitroTransfection

To test the absence of enzymatic activity, a TRAPeze assay wasperformed. As illustrated by FIG. 2, protein lysates from pUF2 or pCDTtransfected cells do not exhibit any telomerase activity. As a positivecontrol, the protein extracts from 293T cells transfected with thenative human TERT were used. Thus the inventors demonstrated that theTERT proteins encoded by either pCDT or pUF2 plasmids do not express anyfunctional enzymatic activity after in vitro transfection.

The inventors have further investigated the intracellular location ofthe two plasmid products of expression. To this aim, an in vitroimmunofluorescence assay was performed. Briefly, 24 h after in-vitrotransfection of 293T cells with either pCDT or pUF2, an anti-V5 antibodycoupled to an Alexa-Fluor labeled secondary antibody were used to detectthe TERT proteins within the cells. The pCDT and pUF2 encoded TERTs werenot detected inside the cell nucleoli contrary to what was observed with293T cells transfected with the plasmid encoding the native human TERT.

To conclude, the inventors demonstrated that after in vitro transfectionwith either pUF2 and pCDT plasmids, first the TERT protein expression isexcluded from the nucleoli and secondly, these products of expression donot exhibit any enzymatic activity. These two criteria establish thesafety of the plasmids and favour their use for in vivo vaccination.

Example 3 In Vivo Immune Response 3.1. Materials and Methods Mice

Female Balb/cBy and C57BL/6J mice (6-8 week old) were purchased fromJanvier laboratories (Saint-Berthevin, France). Animals were housed atthe Specific Pathogen Free animal facility of the Pasteur Institute.Mice were anesthetized prior to intradermal (ID) or intramuscular (IM)immunizations, with a mix solution of xylazine 2% (Rompun, Bayer Sante,Loos, France) and Ketamine 8% (Imalgen 1000, Merial, Lyon, France) inPhosphate Buffer Saline 1× (PBS 1×, Life technologies SAS, Saint-Aubin,France), according to individual animal weight and duration ofanesthesia (intraperitoneal route). All animals were handled in strictaccordance with good animal practice and complied with local animalexperimentation and ethics committee guidelines of the Pasteur Instituteof Paris.

H2 Restricted Peptides

TERT peptides used in mouse studies (IFNγ ELIspot) were predicted byin-silico epitope prediction in order to bind mouse class I MHC,H2K^(b), H2D^(b) or mouse class II H2-IA^(d) using four algorithmsavailable online:

Syfpeithi (http://www.syfpeithi.de/), Bimas(http://www-bimas.cit.nih.gov/), NetMHCpan and SMM(http://tools.immuneepitope.org/main/).

All synthetic peptides were purchased lyophilized (>90% purity) fromProimmune (Oxford, United Kingdom). Lyophilized peptides were dissolvedin sterile water at 2 mg/mL and stored in 35 μL aliquots at −20° C.prior use. Details of peptides sequence and H2 restriction is shown intable 1.

TABLE 1 H2 restricted peptides sequences determinedby in silico prediction algorithms H2D^(b) restricted TERT peptides621-629 (RPIVNMDYI)  621 SEQ ID NO: 10 580-589 (RQLFNSVHL)  580SEQ ID NO: 11 987-996 (TVYMNVYKI)  987 SEQ ID NO: 12H2-IA^(d) restricted TERT peptides 1106-1121 (CLLGPLRAAKAHLSR) 1106SEQ ID NO: 13 1105-1120 (RCLLGPLRAAKAHLS) 1105 SEQ ID NO: 14  951-966 (YSSYAQTSIRSSLTF)  951 SEQ ID NO: 151109-1124 (GPLRAAKAHLSRQLP) 1109 SEQ ID NO: 16

Mice Immunization and In Vivo Electroporation

Intradermal (ID) immunization was performed on the lower part of theflank with Insulin specific needles (U-100, 29GX1/2″-0.33×12 mm, Terumo,Belgium) after shaving. No erythema was observed after shaving, duringand after immunization procedure. Intramuscular immunization (IM) wasperformed in the anterior tibialis cranialis muscle, also using Insulinspecific needles U-100. Each animal received a priming dose of eitherpCDT or pUF2, independently of vaccine route, corresponding to 100 μg ofDNA. All animals were boosted at day 14 post-prime using the same amountof plasmid and the same route of immunization. Directly after IDvaccination, invasive needle electrodes (6×4×2, 47-0050, BTX, USA) areinserted into the skin so that the injection site is placed between thetwo needle rows (the two needle rows are 0.4 cm apart). Two pulses ofdifferent voltages were applied (HV-LV): HV=1125V/cm (2 pulses, 50μs-0.2 μs pulse interval) and LV=250V/cm (8 pulses, 100V-10 ms-20 mspulse interval). Immediately after IM immunization the muscle injectionsite was covered with ultrasonic gel (Labo FH, blue contact gel, NMMedical, France) and surrounded by tweezers electrodes (0.5 cm apart,tweezertrode 7 mm, BTXI45-0488, USA) and voltage was applied using thesame parameters than for skin electroporation. The Agilepulse® in vivosystem electroporator was used for all experiments (BTX, USA). For eachroute of immunization (IM, ID) control mice were treated with the sameprocedures using the same volume of PBS 1×.

Elispot Assay

Briefly, PVDF microplates (IFN-γ Elispot kit, Diaclone, Abcyss, France,10×96 tests, ref. 862.031.010P) were coated overnight with captureantibody (anti-mouse IFN-γ) and blocked with PBS 2% milk. Spleens frompDNA-immunized mice were mashed and cell suspensions were filteredthrough a 70-mm nylon mesh (Cell Strainer, BD Biosciences, France).Ficoll-purified splenocytes (Lymphocyte Separation Medium, Eurobio,France) were numerated using the Cellometer® Auto T4 Plus counter(Ozyme, France) and added to the plates in triplicates at 2×10⁵ or 4×10⁵cells/well and stimulated with 5 μg/ml of cTERT or hyTERT relevantpeptides or Concanavalin A (10 μg/ml), or mock stimulated with serumfree culture medium. After 19 hours, spots were revealed with thebiotin-conjugated detection antibody followed by streptavidin-AP andBCIP/NBT substrate solution. Spots were counted using the ImmunospotELIspot counter and software (CTL, Germany).

In Vivo Cytotoxicity Assay

Briefly, for target cell preparation, splenocytes from naïve C57/Bl6mice were labeled in PBS 1× containing high (5 μM), medium (1 μM) or low(0.2 μM) concentrations of CFSE (Vybrant CFDA-SE cell-tracer kit; Lifetechnologies SAS, Saint-Aubin, France). Splenocytes labeled with 5 and 1μM CFSE were pulsed with 2 different H2 peptides at 5 μg/ml for 1 hourand 30 minutes at room temperature. Peptides 987 and 621 were used forpulsing respectively CFSE high and medium labeled naïve splenocytes.CFSE low labeled splenocytes were left unpulsed. Each mouse previouslyimmunized with either pCDT or pUF2 received at day 10 post-boostinjection 10⁷ CFSE-labeled cells of a mix containing an equal number ofcells from each fraction, through the retro-orbital vein. After 15-18hours, single-cell suspensions from spleens were analyzed by flowcytometry MACSQUANT® cytometer (Miltenyii, Germany).

The disappearance of peptide-pulsed cells was determined by comparingthe ratio of pulsed (high/medium CFSE fluorescence intensity) tounpulsed (low CFSE fluorescence intensity) populations in pDNA immunizedmice versus control (PBS 1× injected) mice. The percentage of specifickilling per test animal was established according to the followingcalculation:

[1−[mean(CFSE^(low)PBS/CFSE^(high/medium)PBS)/(CFSE^(low)pDNA/CFSE^(high/medium)pDNA)]]×100.

Statistical Analysis and Data Handling

Prism-5 software was used for data handling, analysis and graphicrepresentations. Data are represented as the mean±standard deviation.For statistical analyses of ELIspot assays we used a Mann Whitney nonparametric test, and a Kruskal-Wallis analysis with Dunn's multiplecomparison test for in vivo cytotoxicity assay. Significance was set atp-value<0.05.

3.2. Results

pCDT Induces a Strong Cytotoxic CD8 T Cell Response Along with aSpecific CD4 T Cell Response after ID or IM Immunization andElectroporation in Mice

In light of the importance of cytotoxic CD8 T cells in antitumor immuneresponses, the inventors have assessed whether plasmid pCDT was able topromote such an immune response in vivo. Thus, different groups of 9-10C57-Bl/6 mice were immunized with pCDT by ID or IM injection of theplasmid immediately followed by electroporation. Two weeks later, micereceived a boost injection with the same protocol. On day 10 post-boost,mice spleens were harvested and the induced immune response wasmonitored via an IFN-γ ELISPOT assay using H2 restricted peptidesdescribed in Table 1.

Hy-TERT peptides restricted to mouse MHC class I were predicted insilico as described in the material and methods section. As shown inFIG. 3A, a significant augmentation in the frequency of hyTERT specificIFN-γ secreting CD8 T-cells was observed in the spleen of ID and IMvaccinated animals in comparison with control mice. This was observedfor 2 out of 3 class I restricted peptides (p621 and p987, p<0.05). Nosignificant difference in the frequency of specific CD8 T cells wasobserved between IM and ID route for both peptides p921 and p987.

The inventors have further investigated the hyTERT restricted CD4 T cellresponse. To this aim, 9-10 Balb-C mice were immunized with pCDT by IDor IM injection immediately followed by electroporation and the CD4specific T cell response was monitored in the spleen as described beforeusing hyTERT IA^(d) restricted peptides (in silico prediction). Balb-Cmice were chosen because this mouse strain is known to develop good CD4T cell responses. As shown in FIG. 3B, when performing the IFN-γ ELISPOTassay, a significant augmentation in the frequency of hyTERT specificIFN-γ secreting CD4 T-cells was observed in the spleen of ID and IMvaccinated Balb/C mice in comparison with control mice injected with PBS1×. This was observed for 2 out of 3 class I restricted peptides (p1106and p1105, with respectively for p1106 p<0.05 for ID route and p<0.001for IM route and for 1105 the difference was not significant for IDroute and p<0.01 for IM route). No significant difference in thefrequency of specific CD4 T cells was observed between IM and ID routefor both peptides p1105 and p1106.

Thus, pCDT construct is able to promote the expansion of hyTERT specificCD8 and CD4 T-cells in mice. The inventors next wanted to show thathyTERT specific CD8 T-cells exhibit a functional cytotoxic activity invivo, which will be necessary to destroy tumor cells. In order tomeasure the in vivo cytolytic strength of the CD8⁺ T-cell responseelicited by pCDT immunization, the inventors performed an in vivocytotoxicity test using carboxyfluorescein-diacetate succinimidyl ester(CFSE)-labelled, peptide-pulsed splenocytes as target cells. 7 week oldC57/Bl6 mice which received a prime and boost vaccination with pCDT viathe ID or IM route as described before or mock-immunized withphosphate-buffered saline (PBS) were intravenously injected with 10⁷target cells. Target cells were splenocytes from naïve congenic miceseparately labelled with three different concentrations of CFSE andpulsed with individual peptides (p621 or p987) or left un-pulsed as aninternal control. After 15-18 hours, spleen cells were obtained and thedisappearance of peptide-pulsed cells in control versus immunized micewas quantified by fluorescence-activated cell sorting.

Results show that mice develop CTLs against the 2 peptides p621 and p987which were predicted in silico. Peptide 987 gives the strongest in vivolysis. Results were consistent with the ones from the IFN-γ Elispotassays (FIG. 3A). It is worth mentioning that for p621, the mean percentlysis was slightly superior when pCDT was injected via the ID route(mean ID=7.7% vs mean IM=0.2%), however, no significant difference wasobserved between the two routes of immunization.

pUF2 Induces a Strong Cytotoxic CD8 T Cell Response Along with aSpecific CD4 T Cell Response after ID or IM Immunization and EP in Mice

The inventors have further investigated whether the pUF2 plasmid wasable to stimulate the cTERT specific CD8 T cell response in mice. Tothis aim, different groups of 5 C57-Bl/6 mice were immunized with pUF2by ID or IM injection immediately followed by electroporation. Two weekslater, mice received a boost injection with the same protocol. On day 10post-boost, mice spleens were harvested and the induced immune responsewas monitored via an IFN-γ ELISPOT assay using H2 restricted peptidesdescribed in Table 1. cTERT peptides restricted to mouse MHC class Iwere predicted in silico as described in the material and methodssection above. As shown in FIG. 5A, a significant increase in thefrequency of cTERT specific IFN-γ secreting CD8 T-cells was observed inthe spleen of ID and IM vaccinated animals in comparison with controlmice. This was observed for 2 out of 3 class I restricted peptides (p621and p987, with respectively for p621 p<0.05 for ID route and nosignificant difference for IM route and for p687, p<0.001 for ID routeand p<0.01 for IM route). No significant difference in the frequency ofspecific CD8 T cells was observed between IM and ID route for bothpeptides p921 and p987. However, the mean frequency of p987 specific CD8T cells was slightly higher when mice were injected via the ID route, incomparison with the IM route (mean ID=143.2 vs mean IM=54.2). Theinventors have further investigated the cTERT restricted CD4 T cellresponse. To this aim, 9-10 Balb-C mice were immunized ID or IM withpUF2 immediately followed by electroporation and the CD4 specific T cellresponse was monitored in the spleen as described before using cTERTIA^(d) restricted peptides (in silico prediction). Balb-C mice werechosen because this mouse strain is known to develop good CD4 T cellresponses. As shown in FIG. 3B, when performing the IFN-γ ELISPOT assay,a significant augmentation in the frequency of hyTERT specific IFN-γsecreting CD4 T-cells was observed in the spleen of ID and IM vaccinatedBalb-C mice in comparison with control mice injected with PBS 1×. Thiswas observed for the 2 II restricted peptides tested (p1106 and p1105,p<0.01 for ID and IM route). No significant difference in the frequencyof specific CD4 T cells was observed between IM and ID route for bothpeptides p1105 and p1106.

Thus, pUF2 construct is able to promote the expansion of cTERT specificCD8 and CD4 T-cells in mice. We next wanted to show that cTERT specificCD8 T-cells exhibit a functional cytotoxic activity in vivo, which willbe necessary to destroy tumor cells. In order to measure the in vivocytolytic strength of the CD8⁺ T-cell response elicited by pUF2immunization, we performed an in vivo cytotoxicity test usingcarboxyfluorescein-diacetate succinimidyl ester (CFSE)-labelled,peptide-pulsed splenocytes as target cells. 7 week old C57/Bl6 micewhich received a prime and boost vaccination with pUF2 via the ID or IMroute as described before or mock-immunized with phosphate-bufferedsaline (PBS) were intravenously injected with 10⁷ target cells. Targetcells were splenocytes from naïve congenic mice separately labelled withthree different concentrations of CFSE and pulsed with individualpeptides (p621 or p987) or left un-pulsed as an internal control. After15-18 hours, spleen cells were obtained and the disappearance ofpeptide-pulsed cells in control versus immunized mice was quantified byfluorescence-activated cell sorting.

The inventors observed that mice developed CTLs against the 2 peptidesp621 and p987 which had been previously identified in silico. Peptide621 gives the strongest in vivo lysis. These results were concordantwith the ones from the IFN-γ Elispot assays (FIG. 5A). Interestingly, asignificant difference was observed between the two routes ofimmunization for p621. Indeed, for p621, the mean percent lysis wassuperior when pUF2 was injected via the ID route (mean ID=64.5% vs meanIM=11%). A non-significant difference was observed for p987 (meanID=35.7% vs mean IM=21.3%). This confirms that the pUF2 ID vaccinationwould allow generating a stronger and larger CD8 T cell response thatthe IM route.

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1-19. (canceled)
 20. An immunogenic composition comprising a nucleicacid that comprises a sequence encoding (i) a cat telomerase reversetranscriptase (TERT) deprived of telomerase catalytic activity, or (ii)a fragment thereof.
 21. The composition of claim 20, wherein the nucleicacid further encodes a non-cat TERT antigenic fragment.
 22. Thecomposition of claim 20, wherein the nucleic acid is a DNA, preferably aDNA plasmid.
 23. The composition of claim 20, wherein the sequence thatencodes cat TERT contains mutations that provide inactivation of thecatalytic activity.
 24. The composition of claim 23 wherein themutations are a deletion of at least one amino acid.
 25. The compositionof claim 24, wherein the sequence encoding cat TERT is deleted of aminoacids VDD.
 26. The composition of claim 20, wherein the sequenceencoding cat TERT is further deprived of a nucleolar localizationsignal.
 27. The composition of claim 26, wherein the sequence encodingcat TERT is deleted of N-terminal 47 amino acids.
 28. The composition ofclaim 20, wherein the nucleic acid comprises a sequence encoding anantigenic fragment of cat TERT.
 29. The composition of claim 28, whereinthe nucleic acid comprises a sequence encoding an antigenic fragment ofcat TERT which corresponds to at least 80% of cat TERT sequence deletedof N-terminal 47 amino acids.
 30. The composition of claim 28, whereinthe nucleic acid comprises a sequence encoding an antigenic fragment ofcat TERT comprising, or consisting of, SEQ ID NO:7 or
 8. 31. Thecomposition of claim 21, wherein the nucleic acid further comprises asequence that encodes a non-cat TERT antigenic fragment, which non-catTERT antigenic fragment originates from a dog TERT sequence.
 32. Anucleic acid that comprises a sequence encoding (i) a cat TERT deprivedof telomerase catalytic activity, or (ii) an antigenic fragment thereof.33. The nucleic acid of claim 32, which further comprises a non-cat TERTantigenic fragment.
 34. The nucleic acid of claim 32, which encodes aprotein sequence selected from the group consisting of SEQ ID NO: 2, 4,5, 6, 7, and
 8. 35. The nucleic acid of claim 34 which comprises asequence selected from the group consisting of SEQ ID NO: 1, 3, ornucleotides 241-3444, or 439-3444 of SEQ ID NO:1, or nucleotides1414-3297 or 241-3456 of SEQ ID NO:
 3. 36. A method for triggering animmune response in a cat, against cells that overexpress telomerase,which method comprises administering an immunogenic compositioncomprising a nucleic acid that comprises a sequence encoding (i) a cattelomerase reverse transcriptase (TERT) deprived of telomerase catalyticactivity, or (ii) a fragment thereof.
 37. The method of claim 36,wherein the cells that overexpress telomerase are dysplasia cells, tumorcells, or cells infected by an oncovirus.
 38. A method for treating atumor in a cat, which method comprises administering an immunogeniccomposition comprising a nucleic acid that comprises a sequence encoding(i) a cat telomerase reverse transcriptase (TERT) deprived of telomerasecatalytic activity, or (ii) a fragment thereof.
 39. The method of claim38, wherein the tumor is selected from the group consisting of lymphomaor lymphosarcoma (LSA), adenoma, lipoma, myeloproliferative tumor,melanoma, squamous cell carcinoma, mast cell tumor, osteosarcoma,fibrosarcoma, lung tumor, brain tumor, nasal tumor, liver tumor, andmammary tumor.
 40. The method of claim 38, wherein the composition isadministered by intradermal or intramuscular route.
 41. The method ofclaim 38, wherein the composition is administered by electroporation.42. The method of claim 38, wherein the cat is at risk of developing atumor.
 43. The method of claim 38, wherein the cat is healthy but aged.44. The method of claim 36, wherein the immunogenic composition inducesa long term memory immune response.